Extensible beam



May 26, 1970 L. ALZIARI EXTENSIBLE. BEAM 2 Sheets-Sheet 1 Filed July 17, 1968 //VI//1/TO A9.-

May 26,1970 I 1.1 2.111. 3,513,612

EXTENSIBLE BEAM FiledJuly 17, 1968 2 Sheets-Sheet z f1 2" M 'N 2 Lou/3 fizz/am United States Patent Office.

3,513,612 EXTENSIBLE BEAM Louis Alziari, 25 Boulevard Carabacel, Nice, Alpes Maritimes, France Filed July 17, 1968, Ser. No. 745,492 Claims priority, applicagigil7lirance, July 19, 1967,

Int. c1. E04c 5/04,- E04h 11/54 US. Cl. 52-632 2 Claims ABSTRACT OF THE DISCLOSURE The. invention relates to the telescopic beams which are commonly used in the construction of reinforced concrete floors. These beams arefitted with extensions which slide longitudinally so that the length of a unit can be adjusted to the chord between supports. The beam is made up of an upper chord-piece, usually in the shape of an inverted U, connected by two lateral trellises to the lower chord-piece, more often than not made up of two stringers.

The length of the lower chord-piece is shorter than that of the upper chord-piece and the corresponding ends of the two chord-pieces are connected by slanting lateral irons, extending the stringers forming the low chordpiece.

The upper part of the extension is so shaped that it can adapt itself to the upper chord-piece of the beam and guide the two units when one slides in relation to the other.

After adjustment to the required length, the extension is locked in position against the beam so as to make the whole unit continuous.

Locking is elfected by any method of tighteningscrew or wedge-acting on the lower part of the extension, and bearing on a rigid plate fixed on the stringers forming the lower chord-piece of the beam, where they start to extend obliquely.

In the beams currently used, this plate is completely rigid and the slating irons connecting the end of the upper chord-piece of the beam to the corresponding end of the lower chord-piece are formed by extending the two stringers forming the lower chord-piece itself. This construction means that all stresses to which the supporting plate is subjected, resulting both from initial tightening and from the load borne, are transmitted to the lower chord-piece of the beam as well as to the slanting irons extending it.

The invention consists of replacing these irons by two ties the lower part of which is connected, not directly to the stringers forming the lower chord-piece of the beam or to a rigid plate forming a brace between them, but on the contrary at points situated between these stringers, on a comparatively flexible plate replacing the previous I rigid plate.

3,513,612 Patented May 26, 1970 accordance with the invention. FIG. 1 is a side elevation view of the end of a beam with set-in extension. FIGS. 2 and 3 are separate end views of the beam and the extension, while FIG. 4 shows a transversal section of these two units wedged against each other.

It can be seen, FIG. 2, that the upper chord-piece M of the beam is made up of a sheet 1, in the shape of an inverted U, with wings 22. It is connected by web members or trellises 4-4 to the lower chord-piece made up of lower stringers 3-3. FIG. 3 shows that the upper chord-piece M of the extension is made up of a sheet 8, also in the form of an inverted U, with wings 9, and that it is connected by web members or trellises 10 to the lower chord-piece 'M' here shown as an inverted T11. FIGS. 2 and 4 show that a brace plate 5 is welded to the stringers 33, at the end of. the lower chord-piece of the beam, and bears the means of tightening-here the bolt 7itself welded to the ties T.

According to the invention, the brace 5 is comparatively flexible, and the ties T which connect, slantwise, the end X of the lower chord-piece of the beam, by means of the brace plate, to the end Y of the extended upper chord-piece M are welded to this brace at intermediate points between the stringers 3-3, i.e. at points on the brace which follow its movement when it flexes. In the example shown, the contiguous ends of the spaced coplanar plate members are welded and secured on either side of the reinforcements 6 forming the centre of the brace and bearing the internally threaded tightening nut, as is clearly shown in FIG. 2 and 4.

The result of this arrangement, mentioned above, can be explained as follows:

Before placing a load on a beam/extension unit adjusted tothe required length, the bolt 7 is screwed to tighten the two upper chord-pieces M and M against each other, through the intermediary of the lower chordpiece M'., of the extension. When the load is imposed, the extension has a tendency to pivot downwards, in relation to point 0, where it receives the supporting reaction F. Beam/extension contact may then be made at two points X and Y. At Y (end of the extended upper chordpiece M of the beam) the extension applies a force F to the beam. At X, the extension applies a force F1 to the means of tightening 7 borne by the ties T.

Due to the comparative flexibility of the small plate welded to the ties T, this can only transmit an attenuated vertical stress both to the trellis and to the lower chordpiece of the beam, conversely to what would happen with a rigid plate, and the ties T alone bear the tensile stress due to the initial tightening of the bolt 7 and the force F1. This tensile stress on the ties T is transmitted in full, at Y, to the end of the extended upper chord-piece M of the beam. The vertical component of this tensile stress goes to reduce the force F applied by the extension to the beam at Y, which forces, tending to raise the point of contact is translated, if it is not compensated, by considerable flexion of the whole. Finally, for a given geometry of the whole, the actions F and F1 being proportionate, action F and the vertical component of the tensile stress on the ties which counters it remain in the same ratio irrespective of the load.

I claim:

1. In an assembly of a beam and a beam extension longitudinally adjustable within the beam, said beam comprising an upper longitudinal chord, transverselyspaced web members depending from the upper chord, transversely spaced lower stringers carried by the respective web members, the upper chord extending longitudinally beyond the stringers, transversely-spaced ties connecting the end of the upper chord to a cross member on the stringers, said cross memlber comprising a pair of spaced coplanar plate members and an internally threaded tightening nut interposed between said plate members, the ends of the plate members contiguous to said nut being secured thereto and the other ends of said plate members being secured to said stringers, the ends of the ties being joined to said nut, said cross-member being resiliently flexible in the transverse direction of the beam, said tightening nut being positioned centrally in the transverse direction between the points of connection of the crossmember to the stringers, whereby forces exerted by the beam-extension on the tightening nut are transmitted directly to the ties and thus to the end of the upper chord, but are transmitted only indirectly to the stringers through the resilience of the cross-member.

2. An assembly of a beam and a beam-extension, as claimed in claim 1, wherein the beam-extension comprises an upper chord member in the form of a beam of inverted U section, a lower chord member in the form of a beam of inverted T section, and two transversely spaced References Cited UNITED STATES PATENTS 3,008,556 11/1961 Hinze 52632 3,180,463 4/1965 Romek 52632 FOREIGN PATENTS 1,142,665 1957 France. 1,010,484 1965 Great Britain. 1,235,559 1967 Germany.

HENRY C. SUTHERLAND, Primary Examiner US. Cl. X.R. 52645, 693 

